As consumer products become smaller and more portable, they increasingly rely on battery packs, such as rechargeable battery packs, for power sources. Battery packs used in conjunction with portable electronic devices, (such as two-way portable radios, cellular telephones, and computers, to name but a few), typically include a fuse as part of the battery pack. The fuse, such as a thermal fuse, is used to protect the battery cells inside the battery package from becoming too hot during charge or recharge. Overheating of the cells during charging presents a risk to the battery cells which make up the battery pack. Excessive heating can deleteriously affect battery discharge performance and significantly shorten cycle life of the battery pack. In extreme conditions, rapid overcharging of battery cells in a battery pack can result in a catastrophic failure of the battery pack. Malfunctions resulting in catastrophic failure and/or degraded performance include short circuits between the battery cells or malfunctions attributable to the battery charger.
Known fuses for use in battery packs, however, suffer from a substantial number of practical limitations. Current fuses are typically too large and too heavy to be used in small ultra light consumer applications. As the electronics industry moves to smaller and lighter electronic devices, smaller fuses are required.
Another problem inherent in present day state of the art fuse technology, relates to the fact that such fuses are typically made of materials which are fairly brittle, and hence, are subject to breakage upon shock. As consumer electronic devices become smaller and more portable, such devices are increasingly called upon to withstand more shocks, as by dropping the electronic package including the battery pack from a height of up to six feet or more. Accordingly, fuse devices incorporated into battery packages must be capable of withstanding shocks occasioned by, for example, droppage, bumps and impacts.
Accordingly, a need exists for an improved thermal fuse for use in a battery package. Such improved thermal fuse should overcome the limitations of cost and size, as well as being capable of withstanding shocks and bumps occasioned by typical consumer use.